44 lines
1.3 KiB
C++
Executable File
44 lines
1.3 KiB
C++
Executable File
// Copyright 2015, Tobias Hermann and the FunctionalPlus contributors.
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// https://github.com/Dobiasd/FunctionalPlus
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#pragma once
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#include <fplus/container_common.hpp>
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#include <fplus/maybe.hpp>
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namespace fplus
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{
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// API search type: elem_at_float_idx : (Float, [a]) -> a
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// fwd bind count: 1
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// Interpolates linearly between elements.
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// xs must be non-empty.
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template <typename Container,
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typename T = typename Container::value_type>
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T elem_at_float_idx(double idx, const Container& xs)
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{
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assert(is_not_empty(xs));
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if (idx <= 0.0)
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{
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return xs.front();
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}
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std::size_t idx_floor = floor<double, std::size_t>(idx);
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std::size_t idx_ceil = ceil<double, std::size_t>(idx);
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if (idx_ceil >= size_of_cont(xs))
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{
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return xs.back();
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}
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double idx_floor_float = static_cast<double>(idx_floor);
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double idx_ceil_float = static_cast<double>(idx_ceil);
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double weight_floor = idx_ceil_float - idx;
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double weight_ceil = idx - idx_floor_float;
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return
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(weight_floor * elem_at_idx(idx_floor, xs) +
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weight_ceil * elem_at_idx(idx_ceil, xs));
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}
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} // namespace fplus
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